Currently, there are many types of acoustic alarm systems activated upon detection of one or more predetermined events. These alarms are intended to protect the security of homes, automobiles, businesses, etc. and often alert police or specialized security companies of an unlawful entrance of the premises.
Also, it is known to use sensors for identifying potentially dangerous events, such as in smoke alarms, that sound whenever the smoke level in a building increases over a certain threshold. Fires cause approximately two-thirds of known fatalities, with automobile exhaust and faulty heating equipment causing the remaining one-third.
Presence of chemicals dangerous to humans is also alarmed based on chemical reactions. Thus, volatile compounds detectors detect various types of hazardous gases such as carbon monoxide, volatile amines, ammonia, nitrogen dioxide “G-type” nerve agents (sarin, soman and GF). These sensors are used in various types of alarms. It is for example known that CO (Carbon monoxide) is the leading cause of poisoning deaths in the U.S; annually 3,500 to 4,000 die of CO poisoning, and an estimated 10,000 people lose a day's work or seek medical attention.
Carbon monoxide CO is rapidly absorbed by the lungs and quickly passes to the blood, forming carboxyhemoglobin with the blood red cells (hemoglobin). The affinity of CO to hemoglobin is 20-270 times greater than the affinity of oxygen to hemoglobin. Hemoglobin carrying CO is incapable of releasing oxygen to the tissues. Even small amounts of carbon monoxide in the air will quickly increase the percentage of carboxyhemoglobin, reducing significantly the quantity of oxygen carried to the cells. For instance, breathing air with 0.01% (100 ppm) CO for two hours has been shown to increase blood carboxyhemoglobin concentrations to 16.0%, a concentration that will cause CO poisoning symptoms.
The U.S. Environmental Protection Agency reports that the majority of households in Canada and the U.S. are potentially at risk from CO poisoning from at least one hazardous source, e.g. the fireplace.
Recent advances in such areas as nano-technology, micro-electromechanical systems, micro-fluidics, micro-separations and opto-electronics present new technological possibilities for producing fast, extremely sensitive and inexpensive “smart” sensing systems. Advancements in micro-fabrication methods of silicon chips make it possible to produce sensor and biosensor arrays coated with specific sensing components with a high degree of reliability and at a low cost.
Current sensors are able to accurately detect chemical and biological agents at threshold concentrations in a maximum of 5 to 10 minutes. Reviews of the status of commercially available chemical and biological analytical instruments show that the chemical detectors are much more developed than the biological detectors. The chemical detectors are able to provide near real-time information about chemical agents (within seconds or minutes). They generally use transducer technologies including electrochemical, piezoelectric, colorimetric and optical systems.
The biosensors are devices that use biological molecules to detect other biological molecules of chemical substances. Biosensors with the specificity to distinguish target microorganisms in complex samples are also available today. For example, one FSU technology development project uses an instrument for trapping, separation, concentration and assay of bio-agents on the micrometer scale and is based on an AC electrokinetics technique. The operating principle is based on the polarizability of microorganisms, which depends strongly on their composition, morphology, and phenotype. Depending on the frequency of an applied electrical field, separation and detection of different bacteria, including viable and non-viable microorganisms is possible. Some potential benefits of this sensor are high sensitivity, automation, and compactness. Manufacture of pocketsize analyzers is also possible.
Unlike chemical agents, many living biological agents can reproduce, multiply inside the host and be passed from one host to another. The treat of biological weapons has been magnified in recent years due to the advances in the molecular biology, genetic engineering and related technologies as well as in the development of highly efficient delivery and dispersion systems. Both civilian and military sources predict that in the next 10 years, the treat from proliferation of biological weapons will increase dramatically. Early detection and warning methods for biological agents are paramount.
Nano-sensors are extremely small devices capable of detecting and responding to physical stimuli such as movement, light, force, acoustic, thermal, electromagnetic, etc. The stimuli may have dimensions in the order of one billionth of a meter.
There is a need to develop new technologies and systems for ensuring an adequate personal protection against various perils and to provide a prompt response to environmental haphazard, chemical or biological attacks/disasters.